A word often used by anime characters. (Usually the anti-social/ broody/ cold/ tortured types. Ex. Hiei from Yu Yu Hakusho.)

It is a universal bitchy answer to anything anyone says. The character says it when they could care less, or when they are being a jerk. Which is probably all the time. (Can even be used as a greeting, it's pretty versatile. Like grunting to communicate.)

1.) Yusuke: "Hell of an actor. You know not everyone can pretend to laugh at their dying friends."
Hiei: "Hn."

2.) Hiei: "Hn..."
Yusuke: "Damn Hiei, is this how you say hello to people now?!"